Hubble Space Telescope still pushing the frontiers of astronomy

Nearly a quarter of a century after its 1990 launch, the Hubble Space Telescope is still pushing the frontiers of observational astronomy, thanks to the sensitivity of its instruments, the ultra precise way the observatory can be controlled and ingenious new techniques that are allowing astronomers to peer deeper into the cosmos than ever before.

"That's why the Hubble is still so exciting," said Matt Mountain, director of the Space Telescope Science Institute at Johns Hopkins University in Baltimore. "We're learning more and more about how to use it even better and better, whether it's looking for exoplanet atmospheres, measuring dark energy to a precision we never thought possible or using gravitational lenses to push Hubble to look even further back in time."

In recent observations, Hubble has been used to search for dim, difficult-to-detect minor planets beyond the orbit of Pluto, possible candidates for a flyby after theNew Horizons probe streaks past Pluto in 2015. Hubble has monitored Jupiter's Great Red Spot, which appears to be shrinking, and a comet -- Siding Spring -- that will make a close flyby of Mars in October.

But it's Hubble's ability to capture light from galaxies shining when the universe was a fraction of its present age that continues to intrigue scientists and the public alike, providing a glimpse into the depths of cosmic history.

To many astronomers, one of Hubble's most mind-boggling observations was a 1995 time exposure of an apparently empty region of space. The resulting "Hubble Deep Field" image, built up over 10 days, revealed thousands of previously unseen galaxies sprinkled like colored jewels on black velvet.

Similar images using newer, more sensitive instruments have revealed a universe populated by uncounted galaxies and fragments of galaxies that somehow began assembling shortly after the big bang birth of the cosmos 13.7 billion years ago.

Now, 20 years after the original Deep Field, Hubble is making another series of long-exposure photographs known as "Frontier Fields." But this time around,Hubble is using the titanic gravity of galaxies and dark matter in nearby clusters to magnify images of even more remote -- and thus younger -- galaxies in the far background.

The result, astronomers hope, will be a glimpse of the universe when it was only 400 million years old, the age when stars and galaxies first began shining as the infant universe expanded and cooled.

NASA's $8 billion James Webb Space Telescope, scheduled for launch in 2018, is optimized to directly image that early epoch in the infrared region of the spectrum, but Hubble's gravity-assist Frontier Fields may provide a tantalizing preview of what's to come.

"Gravity bends light, that was Einstein's discovery, general relativity, and that cluster of galaxies and dark matter can actually behave like a lens and actually magnify objects behind it in the very distant universe," Mountain said in an interview with CBS News. "That allows Hubble to see things even farther away than it could normally."

The resulting gravitationally magnified images are distorted and smeared into arcs "but if you understand the lens, you can recreate the actual shape back where you're going," Mountain said. "Because of our experience over the last few years, we've worked out how to calculate the prescription of the lens so when we see one of these objects we know now how far away it is and how bright it is, which we wouldn't have known before."

How far away is far? And how old is old?

"It's increasing Hubble's ability to go back in time, in very specific areas, back to about 400 million years after the big bang," Mountain said. "That's the incredible thing, that we've managed to calibrate the prescription of these gravitational lenses and now we can use them as tools. Four or five years ago, that wasn't possible."

Closer to home, both in time and space, the hunt for planets orbiting other stars is one of the hottest fields in astronomy, thanks in large part to NASA's Kepler space telescope, a 50-megapixel camera that has discovered thousands of exoplanet candidates.

Mountain said Hubble is using a new technique to study starlight passing through the atmosphere of a confirmed exoplanet as it moves in front of its parent star to measure at least some of its chemical constituents. The trick is being able to separate out the light passing through an atmosphere from the total output of the vastly brighter star.

• Hubble telescope marks another milestone in space

Simply pointing Hubble at a nearby target star will not work because the starlight will saturate the camera's CCD detector, resulting in a blob-like image that cannot be studied with the required precision.

"The problem here is we have to look at very bright stars, and Hubble is very sensitive," Mountain said. "It basically smears the light over the whole camera. It's a bit like when you've got a digital camera and you look at a street lamp by accident at night and you get a streak across your camera. That's the problem Hubble has when it looks at bright stars.

"So the guys here came up with this really cunning idea. Because Hubble can point so accurately, we actually (move the telescope and) drift the star down the camera all the time so you're producing a very straight, linear streak, but it smears the light over the whole CDD and it doesn't saturate."

The resulting streaks can be precisely measured and subtle changes teased out of the data.

"They found a way to very accurately move the telescope while we took the exposure so the light got spread out in these columns and it didn't saturate the camera," Mountain said. "But because we collect all the light over the exposure, we sum up those streaks and we can see those very, very small differences and actually see for the very first time even fainter planets than we could see before."

So far, Hubble has been able to use the technique with a handful of Jupiter-class planets, but Mountain said he is confident researchers eventually will be able to look for signs of water vapor in Neptune-size worlds as observations improve.

Hunting for bigger game, Nobel Laureate Adam Riess, who earlier used Hubble to help confirm the existence of dark energy and its role in speeding up the expansion of the universe, figured out a way to use the streak-exposure technique to improve cosmic distance measurements by a factor of 10.

He came up with the idea while swimming laps in a Baltimore pool, Mountain said. "He thought, oh my God, I could use this technique to help me with my dark energy research."

To directly measure the distance to a star, it must be close enough to Earth that it shifts position when viewed from one side of Earth's orbit and the other. Hold a finger up at arm's length and look at it with one eye and then the other. The finger will change position slightly due to this parallax effect.

Because the 186-million-mile diameter of Earth's orbit is known, astronomers only need to measure the angular shift of a distant star to calculate how far away it must be. But given the scale of the galaxy, even a 186-million-mile baseline means exceedingly small angles. To directly measure the distance to the nearest star, for example, astronomers had to discern angles equivalent to the width of a dime two miles away.

That star, Alpha Centauri, is just 4 light years from Earth. The disk of the Milky Way spans 100,000 light years and millions to billions of light years separate galaxies.

To extend the distance ladder across the gulfs separating galaxies, astronomers use Cepheid variables, stars that pulsate in a predictable manner and have a known intrinsic brightness. By measuring the apparent brightness of a Cepheid in a distant galaxy, and comparing it to the brightness of a Cepheid a known distance from Earth, astronomers can indirectly calculate the distance to that galaxy.

The key is first directly measuring the parallax of a Cepheid in the Milky Way to calibrate the cosmic distance ladder.

Up to this point, direct measurements of stellar distances using parallax extended a few hundred light years. Using the streak-exposure technique, Riess and co-worker Stefano Casertano were able to directly measure the distance to a Cepheid variable star some 7,500 light years out.

"Inside our own galaxy, instead of just looking at very local objects, we can look very far out," Mountain said. "He has managed to change the measurement precision of the universe from 10 percent, he thinks, down to 2 to 3 percent. Why is that important? Well, it's all about dark energy."

A more accurate distance scale allows a more precise characterization of dark energy's effects on the universe at different times in its evolution, shedding light on how the cosmic expansion is changing and how that plays into the ultimate fate of the universe.

Other spacecraft now in development will probe that new frontier in great detail, but Hubble is helping fill in the blanks today by "using its stability and being very smart with new math and new techniques," Mountain said. "So suddenly we've given Hubble a new ability to measure things 10 times more accurately than it could do before."

Rosetta Closing in on Comet 67P/Churyumov-Gerasimenko after Decade Long Chase

ESA’s Rosetta Spacecraft nears final approach to Comet 67P/Churyumov-Gerasimenko in late July 2014. This collage of imagery from Rosetta combines Navcam camera images at right taken nearing final approach from July 25 to July 31, 2014, with OSIRIS wide angle camera image at left of comet’s coma on July 25 from a distance of around 3000 km. On July 31 Rosetta had approached to within 1327 km. Images to scale and contrast enhanced to show further detail. Credit: ESA/Rosetta/NAVCAM/OSIRIS/MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Collage/Processing: Marco Di Lorenzo/Ken Kremer

The European Space Agency’s (ESA) Rosetta spacecraft is at last rapidly closing in on its target destination, Comet 67P/Churyumov-Gerasimenko, after a decade long chase of 6.4 billion kilometers through interplanetary space. See imagery above and below.

As of today, Friday, August 1, ESA reports that Rosetta has approached the ‘rubber ducky looking’ comet to within a distance of less than 1153 kilometers. That distance narrows with each passing moment as the speeding robotic probe moves closer and closer to the comet while looping around the sun at about 55,000 kilometers per hour (kph).

Rosetta is now just 5 days away from becoming Earth’s first probe ever to rendezvous and enter orbit around a comet.

See above our image collage of Rosetta nearing final approach with the spacecrafts most recent daily Navcam camera images, all taken within the past week starting on July 25 and including up to the most recently release image snapped on July 31. The navcam images are all to scale to give the sense of the spacecraft approaching the comet and revealing ever greater detail as it grows in apparent size in the cameras field of view.

The highest resolution navcam image yet of the two lobed comet – merged at a bright band – was taken on July 31 from a distance of 1327 kilometers and published within the past few hours by ESA today, Aug 1. It shows the best view yet of the surface features of the mysterious bright necked wanderer composed of primordial ice, rock, dust and more.

 The Navcam collage is combined with an OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) wide angle camera view of the comet and its asymmetric coma of ice and dust snapped on July 25 from a distance of around 3000 km, and with an exposure time of 300 seconds. The OSIRIS image covers an area of about 150 x 150 km (90 mi x 90 mi). The images have been contrast enhanced to bring out more detail.

Scientists speculate that the comets bright neck region could be caused by differences in material or grain size or topological effects.

Rosetta’s history making orbital feat is slated for Aug. 6 following the final short duration orbit insertion burns on Aug. 3 and Aug. 6 to place Rosetta into orbit at an altitude of about 100 kilometers (62 miles) where it will study and map the 4 kilometer wide comet for some 17 months.

The comet rotates around once every 12.7 hours.

The coma of Rosetta’s target comet as seen with the OSIRIS wide-angle camera. The image spans 150 km and was taken on 25 July 2014 with an exposure time of 330 seconds. The greyscale relates to the particle density in the coma, with highest density close to the nucleus, becoming more diffuse further away. The hazy circular structure on the right is an artefact. The nucleus is also overexposured. The specks and the streaks in the background are attributed to background stars and cosmic rays. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Crop from the 31 July processed image of comet 67P/Churyumov-Gerasimenko, to focus on the comet nucleus. Credits: ESA/Rosetta/NAVCAM

“If any glitches in space or on ground had delayed the most recent burns, orbital mechanics dictate that we’d only have had a matter of a few days to fix the problem, re-plan the burn and carry it out, otherwise we run the risk of missing the comet,” says Trevor Morley, a flight dynamics specialist at ESOC.

In November 2014 the Rosetta mothership will deploy the Philae science lander for the first ever attempt to land on a comet’s nucleus using harpoons to anchor itself to the surface.

As Rosetta edges closer on its final lap, engineers at mission control at the European Space Operations Centre (ESOC), in Darmstadt, Germany have commanded the probes navigation camera (navcam) to capture daily images while the other science instruments also collect measurements analyzing the comets physical characteristics and chemical composition in detail.

The probe has already discovered that the comet’s surface temperature is surprisingly warm at –70ºC, which is some 20–30ºC warmer than predicted. This indicates the surface is too hot to be covered in ice and must instead have a dark, dusty crust, says ESA.

Comet 67P/Churyumov-Gerasimenko is a short period comet some 555 million kilometres from the Sun at this time, about three times further away than Earth and located between the orbits of Jupiter and Mars.

You can watch the Aug. 6 orbital arrival live via a livestream transmission from ESA’s spacecraft operations centre in Darmstadt, Germany.

While you were reading this the gap between the comet and Rosetta closed to less than 1000 kilometers!

ESA’s Rosetta Spacecraft nears final approach to Comet 67P/Churyumov-Gerasimenko in late July 2014. This image collage from Rosetta combines Navcam camera images taken nearing final approach from July 25 (3000 km distant) to July 31, 2014 (1327 km distant). Top row shows images as seen by spacecraft. Bottom row shows images rotated to same orientation. Images to scale and contrast enhanced to show further detail. Credit: ESA/Rosetta/NAVCAM. Collage/Processing: Marco Di Lorenzo/Ken Kremer

Controversial clues of two 'Goldilocks planets' that might support life are proven false

Mysteries about controversial signals coming from a dwarf star considered to be a prime target in the search for extraterrestrial life now have been solved in research led by scientists at Penn State University. The scientists have proven, for the first time, that some of the signals, which were suspected to be coming from two planets orbiting the star at a distance where liquid water could potentially exist, actually are coming from events inside the star itself, not from so-called "Goldilocks planets" where conditions are just right for supporting life. The study is published by the journal Science in its early online Science Express edition on July 3, 2014, and also in a later print edition of the journal. This image shows the location of the three planets remaining in 2014 after a series of studies since 2004. Research published in 2014, led by Penn State astronomers, shows that two of the signals previously attributed to planets in the habitable zone are actually created by activity within the star itself. The outer (green) planet shown in a companion image dated 2010 also is believed not to exist, based on work by other researchers since 2010. Blue indicates candidate planets in the habitable zone where conditions might be able to support life, orange indicates detections in the too-hot region that is too close to the star.

Mysteries about controversial signals coming from a dwarf star considered to be a prime target in the search for extraterrestrial life now have been solved in research led by scientists at Penn State University. The scientists have proven, for the first time, that some of the signals, which were suspected to be coming from two planets orbiting the star at a distance where liquid water could potentially exist, actually are coming from events inside the star itself, not from so-called "Goldilocks planets" where conditions are just right for supporting life.

The study will be published by the journal Science in its online Science Express issue on July 3, 2014 and in a future print edition of the journal.

"This result is exciting because it explains, for the first time, all the previous and somewhat conflicting observations of the intriguing dwarf star Gliese 581, a faint star with less mass than our Sun that is just 20 light years from Earth," said lead author Paul Robertson, a postdoctoral fellow at Penn State who is affiliated with Penn State's Center for Exoplanets and Habitable Worlds. As a result of this research, the planets now confirmed to be orbiting this dwarf star total exactly three.

"We also have proven that some of the other controversial signals are not coming from two additional proposed Goldilocks planets in the star's habitable zone, but instead are coming from activity within the star itself," said Suvrath Mahadevan, an assistant professor of astronomy and astrophysics at Penn State and a coauthor of the research paper. None of the three remaining planets, whose existence the research confirms, are solidly inside this star system's habitable zone, where liquid water could exist on a rocky planet like Earth.

Astronomers search for exoplanets by measuring shifts in the pattern of a star's spectrum -- the different wavelengths of radiation that it emits as light. These "Doppler shifts" can result from subtle changes in the star's velocity caused by the gravitational tugs of orbiting planets. But Doppler shifts of a star's "absorption lines" also can result from magnetic events like sunspots originating within the star itself -- giving false clues of a planet that does not actually exist. "In the search for low-mass planets," Mahadevan said, "accounting for the subtle signature of a magnetics events in the star is as important as obtaining the highest possible Doppler precision."

The research team made its discovery by analyzing Doppler shifts in existing spectroscopic observations of the star Gliese 581 obtained with the ESO HARPS and Keck HIRES spectrographs. The Doppler shifts that the scientists focused on were the ones most sensitive to magnetic activity. Using careful analyses and techniques, they boosted the signals of the three innermost planets around the star, but "the signals attributed to the existence of the two controversial planets disappeared, becoming indistinguishable from measurement noise," Mahadevan said. "The disappearance of these two signals after correcting for the star's activity indicates that these signals in the original data must have been produced by the activity and rotation of the star itself, not by the presence of these two suspected planets.

"Our improved detection of the real planets in this system gives us confidence that we are now beginning to sufficiently eliminate Doppler signals from stellar activity to discover new, habitable exoplanets, even when they are hidden beneath stellar noise, said Robertson. "While it is unfortunate to find that two such promising planets do not exist, we feel that the results of this study will ultimately lead to more Earth-like planets."

Older stars such as Gliese 581, an "M dwarf" star in the constellation Libra about one-third the mass of our Sun, have until now been considered highly attractive targets in the search for extraterrestrial life because they are generally less active and so are better targets for Doppler observations. "The new result from our research highlights a source of astrophysical noise even with old M dwarfs because the harmonics of the star's rotation can be in the same range as that of its habitable zone, raising the risk of false detections of nonexistent planets," Mahadevan said. "Higher-precision analysis for discovering Earth-like planets using spectrographs will be increasingly more necessary as next-generation spectrographs with the higher Doppler precision needed for detecting important subtle signatures come on line this decade -- like the Habitable Zone Planet Finder (HPF) that our team now is developing at Penn State."

In addition to Mahadevan and Robertson, other coauthors of the research include Penn State Graduate Student Arpita Roy and McDonald Observatory Research Scientist Michael Endl at the University of Texas. Penn State coauthors have affiliations with the Center for Exoplanets and Habitable Worlds and with the Astrobiology Research Consortium, both at Penn State.

Ultrasound for astronomers? A young star's age can be gleamed from nothing but sound waves

In a young region like the so-called Christmas Tree Cluster, stars are still in the process of forming. A star is 'born' once it becomes optically visible (bottom right). During its further evolution, the star contracts and gets smaller in size and hotter until the core temperature is sufficient to start nuclear burning of hydrogen. This marks the end of the stellar childhood phase (bottom left). While the young star evolves from its birth to the beginning of hydrogen burning, its pulsation properties change: the least evolved, i.e., youngest, stars pulsate slower and the most evolved while the oldest stars pulsate faster.

Determining the age of stars has long been a challenge for astronomers. In experiments published in the journal Science, researchers at KU Leuven's Institute for Astronomy show that 'infant' stars can be distinguished from 'adolescent' stars by measuring the acoustic waves they emit.

Stars are often born in clusters, the result of contracting molecular clouds of gas and dust particles. As a star evolves from infant to adolescent, gravitational pull causes it to contract. It gets smaller in size and hotter until the core temperature is sufficient to start nuclear burning of hydrogen. At this point, the star stabilizes and becomes an 'adult'. It stays this way for vast tracts of time.

Determining the age of a young star is far from simple, and knowing which molecular cloud a star comes from gives only a vague idea of its age. But researchers have come up with a way to determine the age of stars by measuring their acoustic vibrations using ultrasound technology similar to that used in the field of medicine.

Acoustic vibrations -- sound waves -- are produced by radiation pressure inside stars. First author Konstanze Zwintz, a postdoctoral researcher at KU Leuven's Institute for Astronomy, and her colleagues studied the vibrations of 34 stars aged under 10 million years and sized between one and four times the mass of our sun.

"Our data shows that the youngest stars vibrate slower while the stars nearer to adulthood vibrate faster. A star's mass has a major impact on its development: stars with a smaller mass evolve slower. Heavy stars grow faster and age more quickly," says Dr. Zwintz.

While theoretical physicists have posited before that young stars vibrate differently than older stars, Zwintz' study is the first to confirm these predications using concrete data from outer space.

"We now have a model that more precisely measures the age of young stars," says Zwintz. "And we are now also able to subdivide young stars according to their various life phases."

The researchers studied the nebula known commonly as the Christmas Tree Cluster. Their data was obtained from the Canadian MOST satellite and the European CoRoT satellite as well as from ground-based facilities such as the European Southern Observatory (ESO) in Chile.

Athena to study the hot and energetic universe

Artist's impression of an active galaxy

The European Space Agency (ESA) has selected the Athena advanced telescope for high-energy astrophysics as its second “large-class” science mission.

The observatory will study the hot and energetic universe and take the “L2” slot in ESA’s Cosmic Vision 2015–25 plan with a launch foreseen in 2028.

By combining a large X-ray telescope with state-of-the-art scientific instruments, Athena will address key questions in astrophysics, including how and why ordinary matter assembles into the galaxies and galactic clusters that we see today as well as how black holes grow and influence their surroundings.

Scientists believe that black holes lurk at the center of almost all galaxies and that they play a fundamental role in their formation and evolution.

To investigate this connection, Athena will observe X-ray emission from very hot material just before it is swallowed by a black hole, measuring distortions due to gravitational light-bending and time-delay effects in this extreme environment. Athena also will be able to determine the spin of the black hole itself.

Athena’s powerful instruments also will allow unprecedented studies of a wide range of astronomical phenomena. These include distant gamma-ray bursts, the hot gas found in the space around clusters of galaxies, the magnetic interplay between exoplanets and their parent stars, Jupiter’s aurorae, and comets in our solar system.

“Athena will be a state-of-the-art observatory that will provide a significant leap forward in scientific capabilities compared with previous X-ray missions and will address fundamental open questions in astrophysics,” said Alvaro Giménez from ESA. “Its selection ensures that Europe’s success in the field of X-ray astronomy is maintained far beyond the lifetime of our flagship observatory, XMM-Newton.”

The selection process for L2 began in March 2013 when ESA issued a call to the European science community to suggest the scientific themes to be pursued by the Cosmic Vision program’s second and third Large missions.

In November 2013, the theme of “the hot and energetic universe” was selected for L2 for a launch in 2028, with “the gravitational universe” selected for L3 and a planned launch in 2034.

Now officially selected for L2, Athena moves into a study phase. Once the mission design and costing have been completed, it will eventually be proposed for “adoption” in around 2019 before the start of construction.

After launch, Athena will travel to its operational orbit around the gravitationally semistable location in space some 1 million miles (1.5 million kilometers) beyond Earth as seen from the Sun — a position coincidentally known as L2. ESA’s Herschel, Planck, and Gaia missions also have used L2 orbits.

Astronomers Discover Rare Triple Supermassive Black Hole System

A team of scientists led by Dr Roger Deane from the University of Cape Town in South Africa has discovered a system of three supermassive black holes – with two of them orbiting each other rather like binary stars – in a galaxy more than 4 billion light-years away from Earth. The discovery could help astronomers in the search for gravitational waves (the ripples in space-time) predicted by Albert Einstein.

Radio images of the triple supermassive black holes system J1502P/SE/SW in the galaxy SDSS J150243.09+1111557.3 and its binary component. Image credit: R.P.Deane et al.

“Einstein’s General Relativity predicts that merging black holes are sources of gravitational waves and in this work we have managed to spot three black holes packed about as tightly together as they could be before spiraling into each other and merging,” said Prof Matt Jarvis from the University of Oxford, who is a co-author of the discovery paper published in the journal Nature.

“The idea that we might be able to find more of these potential sources of gravitational waves is very encouraging as knowing where such signals should originate will help us try to detect these ripples in space-time as they warp the Universe.”

In their study, Dr Deane, Prof Jarvis and co-authors examined six galaxies thought to contain binary supermassive black hole systems.

The astronomers found that one of these galaxies, SDSS J150243.09+1111557.3 (J1502 for short), they thought contained two black holes (J1502P and J1502S) actually contained a triple system with a very compact double supermassive black hole.

They then used the European Very Long Baseline Interferometry Network and the 305-m Arecibo Observatory in Puerto Rico to observe the inner two black holes, J1502SE and J1502SW.

“Very little is actually known about black hole systems that are so close to one another that they emit detectable gravitational waves,” the scientists said.

“This discovery not only suggests that close-pair black hole systems emitting at radio wavelengths are much more common than previously expected,” Prof Jarvis said.

“This exciting discovery perfectly illustrates the power of the Very Long Baseline Interferometry technique, whose exquisite sharpness of view allows us to see deep into the hearts of distant galaxies,” said co-author Dr Keith Grainge from the University of Manchester.

Swiftly moving gas streamer eclipses supermassive black hole

This is the galaxy known as NGC 5548. At its heart, though not visible here, is a supermassive black hole behaving in a strange and unexpected manner. Researchers detected a clumpy gas stream flowing quickly outward and blocking 90 percent of the X-rays emitted by the black hole. This activity could provide insights into how supermassive black holes interact with their host galaxies.

Researchers detected a clumpy gas stream flowing quickly outward and blocking 90 percent of the X-rays emitted by the black hole in NGC 5548.
Astronomers have discovered strange and unexpected behavior around the supermassive black hole at the heart of galaxy NGC 5548. The international team of researchers detected a clumpy gas stream flowing quickly outward and blocking 90 percent of the X-rays emitted by the black hole. This activity could provide insights into how supermassive black holes interact with their host galaxies.

The discovery of the unusual behavior in NGC 5548 is the result of an intensive observing campaign using major European Space Agency and NASA observatories, including the NASA/ESA Hubble Space Telescope. In 2013 and 2014, the international team carried out the most extensive monitoring campaign of an active galaxy ever conducted.

There are other galaxies that show gas streams near a black hole, but this is the first time that a stream like this has been seen to move into the line of sight.

The researchers say that this is the first direct evidence for the long-predicted shielding process that is needed to accelerate powerful gas streams, or winds, to high speeds. “This is a milestone in understanding how supermassive black holes interact with their host galaxies,” said Jelle Kaastra of the SRON Netherlands Institute for Space Research. “We were very lucky. You don’t normally see this kind of event with objects like this. It tells us more about the powerful ionized winds that allow supermassive black holes in the nuclei of active galaxies to expel large amounts of matter. In larger quasars than NGC 5548, these winds can regulate the growth of both the black hole and its host galaxy.”

As matter spirals down into a black hole, it forms a flat disk known as an accretion disk. The disk is heated so much that it emits X-rays near the black hole and less energetic ultraviolet radiation farther out. The ultraviolet radiation can create winds strong enough to blow gas away from the black hole, which otherwise would have fallen into it. But the winds only come into existence if their starting point is shielded from X-rays.

Earlier observations had seen the effects of both X-rays and ultraviolet radiation on a region of warm gas far away from the black hole, but these most recent observations have shown the presence of a new gas stream between the disk and the original cloud. The newly discovered gas stream in the archetypal Seyfert galaxy (NGC 5548) — one of the best-studied sources of this type over the past half-century — absorbs most of the X-ray radiation before it reaches the original cloud, shielding it from X-rays and leaving only the ultraviolet radiation. The same stream shields gas closer to the accretion disk. This makes the strong winds possible, and it appears that the shielding has been going on for at least three years.

Directly after Hubble had observed NGC 5548 on June 22, 2013, the team discovered unexpected features in the data. “There were dramatic changes since the last observation with Hubble in 2011. We saw signatures of much colder gas than was present before, indicating that the wind had cooled down, due to a strong decrease in the ionizing X-ray radiation from the nucleus,” said team member Gerard Kriss of the Space Telescope Science Institute in Baltimore.

After combining and analyzing data from the six observatories involved, the team was able to put the pieces of the puzzle together. NGC 5548’s persistent wind, which scientists have known about for two decades, reaches velocities exceeding 2.2 million mph (3.5 million km/h). But a new wind has arisen that is much stronger and faster than the persistent wind.

“The new wind reaches speeds of up to 18 million km/h [11 million mph] but is much closer to the nucleus than the persistent wind,” said Kaastra. “The new gas outflow blocks 90 percent of the low-energy X-rays that come from close to the black hole, and it obscures up to a third of the region that emits the ultraviolet radiation at a distance of a few light-days from the black hole.”

Strong X-ray absorption by ionized gas has been seen in several other sources, and it has been attributed for instance to passing clouds. “However, in our case, thanks to the combined XMM-Newton and Hubble data, we know this is a fast stream of outflowing gas very close to the nucleus,” said Massimo Cappi of INAF-IASF Bologna. “It may even originate from the accretion disk,” added team member Pierre-Olivier Petrucci of CNRS, IPAG Grenoble.

Swift satellite tallies water production of Mars-bound comet

This composite of C/2013 A1 (Siding Spring) merges Swift UVOT images taken between May 27 and 29, 2014. Sunlight reflected from the comet's dust, which produces most of the light in this image, appears yellow; violet shows ultraviolet light produced by hydroxyl (OH), a molecular fragment of water.

Observations reveal how rapidly Comet Siding Spring is producing water and allow astronomers to better estimate its size.
In late May, NASA’s Swift satellite imaged comet Siding Spring, which will brush astonishingly close to Mars later this year. These optical and ultraviolet observations are the first to reveal how rapidly the comet is producing water and allow astronomers to better estimate its size.

“Comet Siding Spring is making its first passage through the inner solar system and is experiencing its first strong heating from the Sun,” said Dennis Bodewits from the University of Maryland, College Park (UMCP). “These observations are part of a two-year-long Swift campaign to watch how the comet’s activity develops during its travels.”

“Fresh” comets like Siding Spring, which is formally known as C/2013 A1, contain some of the most ancient material scientists can study. The solid part of a comet, called its nucleus, is a clump of frozen gases mixed with dust and is often described as a “dirty snowball.” Comets cast off gas and dust whenever they venture near enough to the Sun.

What powers this activity is the transformation of frozen material from solid ice to gas, a process called sublimation. As the comet approaches the Sun and becomes heated, different gases stream from the nucleus, carrying with them large quantities of dust that reflect sunlight and brighten the comet. By about two and a half times Earth’s distance from the Sun (2.5 astronomical units, or AU), the comet has warmed enough that water becomes the primary gas emitted by the nucleus.

Between May 27 and 29, Swift’s Ultraviolet/Optical Telescope (UVOT) captured a sequence of images as Comet Siding Spring cruised through the constellation Eridanus at a distance of about 229 million miles (368 million kilometers) from the Sun. While the UVOT cannot detect water molecules directly, it can detect light emitted by fragments formed when ultraviolet sunlight breaks up water, specifically hydrogen atoms and hydroxyl (OH) molecules.

“Based on our observations, we calculate that at the time of the observations the comet was producing about 2 billion billion billion water molecules, equivalent to about 13 gallons or 49 liters, each second,” said Tony Farnham from UMCP. At this rate, Comet Siding Spring could fill an Olympic-size swimming pool in about 14 hours. Impressive as it sounds, though, this is relatively modest water emission compared to other comets Swift has observed.

Based on these measurements, the team concludes that the icy nucleus of Comet Siding Spring is only about 2,300 feet (700 meters) across, placing it at the lower end of a size range estimated from earlier observations by other spacecraft.

The comet makes its closest approach to Mars on October 19, passing just 86,000 miles (138,000km) from the Red Planet — so close that gas and dust in the outermost reaches of the comet’s atmosphere, or coma, will interact with the atmosphere of Mars.

For comparison, the closest recorded Earth approach by a comet was by the now-defunct Comet Lexell, which on July 1, 1770, swept to within 1.4 million miles (2.3 million km), or about six times farther than the Moon. During its Mars flyby, Comet Siding Spring will pass more than 16 times closer than this.

Scientists have established that the comet poses no danger to spacecraft now in orbit around Mars. These missions will be pressed into service as a provisional comet observation fleet to take advantage of this unprecedented opportunity.

The Swift observations are part of a larger study to investigate the activity and evolution of new comets, which show distinct brightening characteristics as they approach the Sun not seen in other comets. Bodewits and his colleagues single out comets that can be observed by Swift at distances where water has not yet become the primary gas and repeatedly observe them as they course through the inner solar system. This systematic study will help astronomers better understand how comet activity changes with repeated solar heating.

Molecule vital for creating water exists in dying sun-like stars

Herschel image of the Helix Nebula using the SPIRE instrument at wavelengths around 250 micrometres, superimposed on Hubble image of the nebula. The spectrum corresponds to the outer region of the Helix Nebula outlined on the SPIRE image. It identifies the OH+ molecular ion, which is needed for the formation of water. ESA’s Herschel space observatory is the first to detect this molecule in planetary nebulas – the product of dying Sun-like stars.

Using ESA's Herschel space observatory, astronomers have discovered that a molecule vital for creating water exists in the burning embers of dying Sun-like stars.

When low- to middleweight stars like our Sun approach the end of their lives, they eventually become dense, white dwarf stars. In doing so, they cast off their outer layers of dust and gas into space, creating a kaleidoscope of intricate patterns known as planetary nebulas.

These actually have nothing to do with planets, but were named in the late 18th century by astronomer William Herschel, because they appeared as fuzzy circular objects through his telescope, somewhat like the planets in our Solar System.

Over two centuries later, planetary nebulas studied with William Herschel's namesake, the Herschel space observatory, have yielded a surprising discovery.

Like the dramatic supernova explosions of weightier stars, the death cries of the stars responsible for planetary nebulas also enrich the local interstellar environment with elements from which the next generations of stars are born.

While supernovas are capable of forging the heaviest elements, planetary nebulas contain a large proportion of the lighter 'elements of life' such as carbon, nitrogen, and oxygen, made by nuclear fusion in the parent star.

A star like the Sun steadily burns hydrogen in its core for billions of years. But once the fuel begins to run out, the central star swells into a red giant, becoming unstable and shedding its outer layers to form a planetary nebula.

The remaining core of the star eventually becomes a hot white dwarf pouring out ultraviolet radiation into its surroundings.

This intense radiation may destroy molecules that had previously been ejected by the star and that are bound up in the clumps or rings of material seen in the periphery of planetary nebulas.

The harsh radiation was also assumed to restrict the formation of new molecules in those regions.

But in two separate studies using Herschel astronomers have discovered that a molecule vital to the formation of water seems to rather like this harsh environment, and perhaps even depends upon it to form. The molecule, known as OH+, is a positively charged combination of single oxygen and hydrogen atoms.

In one study, led by Dr Isabel Aleman of the University of Leiden, the Netherlands, 11 planetary nebulas were analysed and the molecule was found in just three.

What links the three is that they host the hottest stars, with temperatures exceeding 100,000ºC.

"We think that a critical clue is in the presence of the dense clumps of gas and dust, which are illuminated by UV and X-ray radiation emitted by the hot central star," says Dr Aleman.

"This high-energy radiation interacts with the clumps to trigger chemical reactions that leads to the formation of the molecules."

Meanwhile, another study, led by Dr Mireya Etxaluze of the Instituto de Ciencia de los Materiales de Madrid, Spain, focused on the Helix Nebula, one of the nearest planetary nebulas to our Solar System, at a distance of 700 light years.

The central star is about half the mass of our Sun, but has a far higher temperature of about 120,000ºC. The expelled shells of the star, which in optical images appear reminiscent of a human eye, are known to contain a rich variety of molecules.

Herschel mapped the presence of the crucial molecule across the Helix Nebula, and found it to be most abundant in locations where carbon monoxide molecules, previously ejected by the star, are most likely to be destroyed by the strong UV radiation.

Once oxygen atoms have been liberated from the carbon monoxide, they are available to make the oxygen-hydrogen molecules, further bolstering the hypothesis that the UV radiation may be promoting their creation.

The two studies are the first to identify in planetary nebulas this critical molecule needed for the formation of water, although it remains to be seen if the conditions would actually allow water formation to proceed.

"The proximity of the Helix Nebula means we have a natural laboratory on our cosmic doorstep to study in more detail the chemistry of these objects and their role in recycling molecules through the interstellar medium," says Dr Etxaluze.

"Herschel has traced water across the Universe, from star-forming clouds to the asteroid belt in our own Solar System," says Göran Pilbratt, ESA's Herschel project scientist.

"Now we have even found that stars like our Sun could contribute to the formation of water in the Universe, even as they are in their death throes."

"Herschel planetary nebula survey (HerPlaNS). First detection of OH⁺ in planetary nebulae," by I. Aleman et al., and "Herschel spectral-mapping of the Helix Nebula (NGC 7293): extended CO photodissociation and OH⁺ emission," by M. Etxaluze et al., are published in Astronomy & Astrophysics.

HerPlaNS (The Herschel Planetary Nebulae Survey) is a survey of 11 planetary nebulas aiming the study the formation and evolution of the circumstellar material by tracing the dust and gas components. The HerPlaNS team is led by Toshiya Ueta from the University of Denver.

The MESS (Mass loss of Evolved StarS) consortium studies a wide variety of evolved stars (including planetary nebulas) to better understand the mass loss in these objects, the dust and gas chemistry in the ejected material, and the processes shaping the nebulae. The MESS consortium is led by Martin Groenewegen (Royal Observatory of Belgium) and the study of planetary nebulas within the group is led by Peter van Hoof (Royal Observatory of Belgium).

Giant telescopes pair up to image near-Earth asteroid

NASA scientists used Earth-based radar to produce these sharp views of the asteroid designated 2014 HQ124 on June 8, 2014.

NASA scientists using Earth-based radar have produced sharp views of a recently discovered asteroid as it slid silently past our planet. Captured on June 8, 2014, the new views of the object designated 2014 HQ124 are some of the most detailed radar images of a near-Earth asteroid ever obtained.

Scientists Marina Brozovic and Lance Benner of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, led the radar observations. The researchers worked closely with Michael Nolan, Patrick Taylor, Ellen Howell, and Alessondra Springmann at Arecibo Observatory in Puerto Rico to plan and execute the observations.

2014 HQ124 appears to be an elongated, irregular object that is at least 1,200 feet (370 meters) wide on its long axis. “This may be a double object, or ‘contact binary,’ consisting of two objects that form a single asteroid with a lobed shape,” Benner said. The images reveal a wealth of other features, including a puzzling pointy hill near the object’s middle, on top as seen in the images.

The 21 radar images were taken over a span of 4.5 hours. During that interval, the asteroid rotated a few degrees per frame, suggesting its rotation period is slightly less than 24 hours.

At its closest approach to Earth on June 8, the asteroid came within 776,000 miles (1.25 million kilometers), or slightly more than three times the distance to the Moon. Scientists began observations of 2014 HQ124 shortly after the closest approach when the asteroid was between about 864,000–902,000 miles (1.39–1.45 million kilometers) from Earth.

Each image in the collage and movie represents 10 minutes of data.

The new views show features as small as about 12 feet (3.75 meters) wide. This is the highest resolution currently possible using scientific radar antennas to produce images. Such sharp views for this asteroid were made possible by linking together two giant radio telescopes to enhance their capabilities.

To obtain the new views, researchers paired the 230-foot (70m) Deep Space Network antenna at Goldstone, California, with two other radio telescopes, one at a time. Using this technique, the Goldstone antenna beams a radar signal at an asteroid and the other antenna receives the reflections. The technique dramatically improves the amount of detail that can be seen in radar images.

To image 2014 HQ124, the researchers first paired the large Goldstone antenna with the 1,000-foot (305m) Arecibo radio telescope in Puerto Rico. They later paired the large Goldstone dish with a smaller companion, a 112-foot (34m) antenna, located about 20 miles (32km) away.

A recent equipment upgrade at Arecibo enabled the two facilities to work in tandem to obtain images with this fine level of detail for the first time.

“By itself, the Goldstone antenna can obtain images that show features as small as the width of a traffic lane on the highway,” said Benner. “With Arecibo now able to receive our highest-resolution Goldstone signals, we can create a single system that improves the overall quality of the images.”

The first five images in the new sequence — the top row in the collage — represent the data collected by Arecibo and are 30 times brighter than what Goldstone can produce observing on its own.

Scientists were fortunate to be able to make these radar observations at all, as this particular asteroid was only recently discovered. NASA’s NEOWISE mission, a space telescope adapted for scouting the skies for the infrared light emitted by asteroids and comets, first spotted the space rock April 23, 2014.

For asteroids, as well as comets, radar is a powerful tool for studying the objects’ sizes, shapes, rotation, surface features, and orbits. Radar measurements of asteroid distances and velocities enable researchers to compute orbits much further into the future than if radar observations were not available.

NASA detects, tracks, and characterizes asteroids and comets passing close to Earth using both ground- and space-based telescopes. The Near-Earth Object Program, commonly called “Spaceguard,” discovers these objects, characterizes a subset of them, and identifies their orbits to determine if any could be potentially hazardous to our planet. To date, U.S. assets have discovered more than 98 percent of the known near-Earth objects.

Along with the resources NASA puts into understanding asteroids, it also partners with other U.S. government agencies, university-based astronomers, and space science institutes across the country that are working to find, track, and understand these objects better. In addition, NASA values the work of numerous highly skilled amateur astronomers, whose accurate observational data helps improve asteroid orbits after they are found.